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Date:   Mon, 3 Dec 2018 10:28:09 +0100
From:   Maxime Ripard <maxime.ripard@bootlin.com>
To:     Hao Zhang <hao5781286@gmail.com>
Cc:     Mark Rutland <mark.rutland@arm.com>,
        Rob Herring <robh+dt@kernel.org>, wens@csie.org,
        Mike Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@codeaurora.org>, thierry.reding@gmail.com,
        linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
        linux-pwm@vger.kernel.org, linux-sunxi@googlegroups.com
Subject: Re: [PATCH v3 1/6] Documentation: ARM: sunxi: pwm: add Allwinner
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Hi!

(Please keep all the recipiens in Cc)

On Sun, Dec 02, 2018 at 12:13:21AM +0800, Hao Zhang wrote:
> Maxime Ripard <maxime.ripard@bootlin.com> =E4=BA=8E2018=E5=B9=B411=E6=9C=
=8827=E6=97=A5=E5=91=A8=E4=BA=8C =E4=B8=8B=E5=8D=886:33=E5=86=99=E9=81=93=
=EF=BC=9A
> >
> > On Tue, Nov 27, 2018 at 09:35:23AM +0100, Uwe Kleine-K=C3=B6nig wrote:
> > > Hello,
> > >
> > > On Tue, Nov 27, 2018 at 08:52:26AM +0100, Maxime Ripard wrote:
> > > > On Mon, Nov 26, 2018 at 12:18:59AM +0800, Hao Zhang wrote:
> > > > > +  - clocks: From common clock binding, handle to the parent cloc=
k.
> > > > > +  - clock-names: Must contain the clock names described just abo=
ve.
> > > >
> > > > [...]
> > > >
> > > > You seem to have used mux-0 and mux-1 for the clock names. I guess =
we
> > > > don't have to use a name there, we can simply use the position to f=
ind
> > > > out (as long as it's documented in the binding)
> > >
> > > I also wondered if the driver relies on the fact that the second clock
> > > is the faster running one. Is this sensible?
> >
> > Not really, I'm not sure we can make those expectations in the DT
> > binding, especially since clock rate can change at runtime.
>
> How about just add one clock on DT, most of the time, 24MHZ is enough
> (apb1 is 100MHZ)
> other one just use as a optional.
> clock rate change at runtime would make the same pair pwm channel
> uncontrollable,
> because previous one would be change by the new one different setting.

The DT is a hardware representation. If the hardware block can use
both clocks, it should be described.

Now, you can totally use only one clock of these 2 in your driver if that's
easier / more reasonable.

Maxime

--=20
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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